The present invention relates to a thermal head for use in video printers, handy printers, facsimiles or the like. More particularly, the invention relates to a thermal head of an end-heating type in which a front end of a non-conductive substrate having thereon a plurality of heat-generating resistors is adapted to be held in sliding contact with a recording medium to effect printing.
Generally, a thermal head for use in printers or fascimiles basically comprises a non-conductive substrate adapted to be held in sliding contact with the recording medium. A plurality of heat-generating resistors for forming heat-generating dots and electrodes for feeding electricity to the heat-generating resistors are formed on the surface of the non-conductive substrate. In order to decrease the manufacturing cost of thermal heads, it is desirable to form such heat-generating resistors and electrodes by a film formation process utilizing photolithography.
There has been known a thermal head of a plain surface-heating type in which a plain surface of a non-conductive substrate having thereon a plurality of heat-generating resistors is adapted to be held in sliding contact with a recording medium to effect printing. In the plain surface-heating type thermal head, it is easy to form such heat-generating resistors and electrodes on the plain surface of the non-conductive substrate by a film pattern formation process utilizing photolithography. However, the thermal head of this type has the following disadvantages:
(1) Distribution of pressure acting on a recording medium such as ink ribbon from the thermal head is apt to become uneven, resulting in deterioration of quality of printed picture, particularly in an image printer of a dye transfer type;
(2) It is difficult to effect print on a plain recording medium;
(3) It is difficult to construct a multi-thermal head for color printing; and
(4) Configuration of non-conductive substrate depends on the diameter of a platen roller.
There has also been known a thermal head of an end-heating type which can eliminate the above-mentioned disadvantages of the thermal head of the plain surface-heating type.
However, in a thermal head of an end-heating type, it is very difficult to directly form such heat-generating resistors and electrodes in the form of three-dimentional configuration on the surface of the non-conductive substrate within the region from the front end through the upper or under side of the non-conductive substrate.
An exemplary thermal head of an end-heating type is decribed in Japanese Unexamined Utility Model Publication (KOKAI) No. 63-125544. In this construction, a plurality of heat-generating resistors and electrodes can be formed on a plain flexible sheet by a film formation process. However, then, the flexible sheet has to be bended in the form of a U-shape and secured on the the upper and under sides and the front end of the non-conductive substrate so as to place the heat-generating resistors on the front end of the non-conductive substrate, resulting in increase of the number of manufacturing process of the thermal head.